They are not hard to set up even for temp use. It is really easy for someone to drop a tab that is tethered by a cord. Any user that picks that option will regret doing so.
I didn't see people picking them up at the wine show. They were set on bar-height counters where they had bottles on display, and the iPad leashes ran behind the counters, so I didn't see the whole setup. It looked like people were just flipping the screens on the counters. Maybe there was enough play to pick them up, but I gather that that depends on how much play there is between the iPad and whatever you tether to. Everyone had a wineglass in hand, so picking up would've made it hard to flip the screen.